This invention relates to an ink jet printing method. More particularly, this invention relates to an ink jet printing method employing a recording element containing coated particles.
In a typical ink jet recording or printing system, ink droplets are ejected from a nozzle at high speed towards a recording element or medium to produce an image on the medium. The ink droplets, or recording liquid, generally comprise a recording agent, such as a dye or pigment, and a large amount of solvent. The solvent, or carrier liquid, typically is made up of water, an organic material such as a monohydric alcohol, a polyhydric alcohol or mixtures thereof.
An ink jet recording element typically comprises a support having on at least one surface thereof an ink-receiving or image-forming layer, and includes those intended for reflection viewing, which have an opaque support, and those intended for viewing by transmitted light, which have a transparent support.
While a wide variety of different types of image-recording elements for use with ink jet devices have been proposed heretofore, there are many unsolved problems in the art and many deficiencies in the known products which have limited their commercial usefulness.
It is well known that in order to achieve and maintain photographic-quality images on such an image-recording element, an ink jet recording element must:
Be readily wetted so there is no puddling, i.e., coalescence of adjacent ink dots, which leads to non-uniform density
Exhibit no image bleeding
Exhibit the ability to absorb high concentrations of ink and dry quickly to avoid elements blocking together when stacked against subsequent prints or other surfaces
Exhibit no discontinuities or defects due to interactions between the support and/or layer(s), such as cracking, repellencies, comb lines and the like
Not allow unabsorbed dyes to aggregate at the free surface causing dye crystallization, which results in bloom or bronzing effects in the imaged areas
Have an optimized image fastness to avoid fade from contact with water or radiation by daylight, tungsten light, or fluorescent light
An ink jet recording element that simultaneously provides an almost instantaneous ink dry time and good image quality is desirable. However, given the wide range of ink compositions and ink volumes that a recording element needs to accommodate, these requirements of ink jet recording media are difficult to achieve simultaneously.
Ink jet recording elements are known that employ porous or non-porous single layer or multilayer coatings that act as suitable image receiving layers on one or both sides of a porous or non-porous support. Recording elements that use non-porous coatings typically have good image quality but exhibit poor ink dry time. Recording elements that use porous coatings typically contain colloidal particulates and have poorer image quality but exhibit superior dry times.
While a wide variety of different types of porous image-recording elements for use with ink jet printing are known, there are many unsolved problems in the art and many deficiencies in the known products which have severely limited their commercial usefulness. The challenge of making a porous image recording layer is to achieve a high gloss level without cracking, high color density, and a fast drying time.
U.S. Pat. No. 5,576,088 relates to an ink jet recording element wherein a gloss providing layer containing an inorganic filler and a latex is coated on top of an ink receiving layer. However, there is a problem with this element in that the drying time is slow and there is a tendency for the layer to exhibit cracks.
It is an object of this invention to provide an ink jet printing method using an ink jet recording element that has a fast ink dry time. It is another object of this invention to provide an ink jet printing method using an ink jet recording element that has good image quality.
These and other objects are achieved in accordance with the invention which comprises an ink jet printing method, comprising the steps of:
A) providing an ink jet printer that is responsive to digital data signals;
B) loading the printer with ink-receptive elements comprising a substrate having thereon an image-receiving layer comprising an inorganic filler and coated particles comprising a polymeric hard core-polymeric soft shell latex, the Tg of the polymeric hard core material being greater than about 60xc2x0 C., the Tg of the polymeric soft shell material being less than about 20xc2x0 C., and the inorganic filler being present in the image-receiving layer in an amount of from about 50 to about 95% by weight;
C) loading the printer with an ink jet ink composition; and
D) printing on the ink-receptive element using the ink jet ink in response to the digital data signals.
The ink jet recording element obtained by the method of the invention provides a fast ink dry time and good image quality.
The substrate used in the invention may be porous such as paper or non-porous such as resin-coated paper; synthetic paper, such as Teslin(copyright) or Tyvek(copyright); an impregnated paper such as Duraform(copyright); cellulose acetate or polyester films. The surface of the substrate may be treated in order to improve the adhesion of the image-receiving layer to the support. For example, the surface may be corona discharge treated prior to applying the image-receiving layer to the support. Alternatively, an under-coating or subbing layer, such as a layer formed from a halogenated phenol or a partially hydrolyzed vinyl chloride-vinyl acetate copolymer, can be applied to the surface of the support.
As described above, the image-receiving layer employed in the process of the invention contains an inorganic filler and a polymeric latex. Any inorganic filler may be used in the invention, such as metal oxides or hydroxides. In a preferred embodiment of the invention, the metal oxide is silica, alumina, zirconia or titania. In another preferred embodiment of the invention, the particle size of the filler is from about 5 nm to about 1000 nm.
The coated particles comprising a polymeric hard core-polymeric soft shell latex used in the process of the invention comprises polymeric particles having a core of material having a relatively high Tg which is coated with another polymer having a relatively low Tg. Core-shell latexes used in the invention may be prepared by emulsion polymerization are described in xe2x80x9cEmulsion Polymerization and Emulsion Polymersxe2x80x9d, edited by P. A. Lovell and M. S. El-Aassar, John Wiley and Sons, 1997.
The core material polymer used in the process of the invention has a Tg of at least about 60xc2x0 C., preferably from about 60xc2x0 C. to about 150xc2x0 C. Examples of these polymers include poly(methylmethacrylate), poly(styrene), poly(p-methylstyrene), poly(t-butylacrylamide), poly(styrene-co-methylmethacrylate), poly(styrene-co-t-butylacrylamide), poly(methylmethacrylate-co-t-butylacrylamide), and homopolymers derived from p-cyanophenyl methacrylate, pentachlorophenyl acrylate, methacrylonitrile, isobornyl methacrylate, phenyl methacrylate, acrylonitrile, isobornyl acrylate, p-cyanophenyl acrylate, 2-chloroethyl acrylate, 2-chloroethyl methacrylate, 2-naphthyl acrylate, n-isopropyl acrylamide, 1-fluoromethyl methacrylate, isopropyl methacrylate, and 2-hydroxypropyl methacrylate. In a preferred embodiment of the invention, the core polymer is poly(methylmethacrylate), poly(styrene), poly(p-methylstyrene), poly(t-butylacrylamide) or poly(styrene-co-methylmethacrylate).
The shell material polymer used in the element employed in the process of the invention has a Tg of about 20xc2x0 C. or lower, preferably from about xe2x88x9250xc2x0 C. to about 20xc2x0 C. Examples of these soft shell polymers which may be used in the invention include homo- and copolymers derived from the following monomers: n-butyl acrylate, n-ethylacrylate, 2-ethylhexylacrylate, methoxyethylacrylate, methoxyethoxy-ethylacrylate, ethoxyethylacrylate, ethoxyethoxyethylacrylate, 2-ethylhexyl-methacrylate, n-propylacrylate, hydroxyethylacrylate, etc. and cationic monomers such as a salt of trimethylammoniumethyl acrylate and trimethylammoniumethyl methacrylate, a salt of triethylammoniumethyl acrylate and triethylammonium-ethyl methacrylate, a salt of dimethylbenzylammoniumethyl acrylate and dimethylbenzylammoniumethyl methacrylate, a salt of dimethylbutylammonium-ethyl acrylate and dimethylbutylammoniumethyl methacrylate, a salt of dimethylhexylammoniumethyl acrylate and dimethylhexylammoniumethyl methacrylate, a salt of dimethyloctylammoniumethyl acrylate and dimethyloctyl-ammoniumethyl methacrylate, a salt of dimethyldodeceylammoniumethyl acrylate and dimethyldocecylammoniumethyl methacrylate, a salt of dimethyloctadecyl-ammoniumethyl acrylate and dimethyloctadecylammoniumethyl methacrylate, etc. Salts of these cationic monomers which can be used include chloride, bromide, methylsulfate, triflate, etc.
Examples of these shell material polymers include poly(n-butylacrylate-co-vinylbenzyltrimethylammonium chloride), poly(n-butylacrylate-co-vinylbenzyltrimethylammonium bromide), poly(n-butylacrylate-co-vinylbenzyldimethylbenzylammonium chloride) and poly(n-butylacrylate-co-vinylbenzyldimethyloctadecylammonium chloride). In a preferred embodiment of the invention, the shell polymer can be poly(n-butyl acrylate), poly(2-ethylhexyl acrylate) poly(methoxyethylacrylate), poly(ethoxy-ethylacrylate), poly(n-butylacrylate-co-trimethylammoniumethyl acrylate), poly(n-butylacrylate-co-trimethylammoniumethyl methacrylate) or poly(n-butylacrylate-co-vinylbenzyltrimethylammonium chloride).
Following are examples of coated particles of polymeric soft shell-polymeric hard core materials which can be used in the process of the invention:
An additional binder can also be used in the image-recording layer employed in the process of the invention, e.g., a water soluble polymer such as poly(vinyl alcohol), gelatin, poly(vinyl pyrrolidone), poly(2-ethyl-2-oxazoline), poly(2methyl-2-oxazoline), poly(acrylamide), Chitosan, methylcellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, etc. Other binders can also be used such as low Tg polymer latexes such as poly(styrene-co-butadiene), a polyurethane latex, a polyester latex, poly(n-butyl acrylate), poly(n-butyl methacrylate), poly(2-ethylhexyl acrylate), a copolymer of n-butylacrylate and ethylacrylate, a copolymer of vinylacetate and n-butylacrylate, etc.
Other additives may also be included in the image-recording layer such as pH-modifiers like nitric acid, cross-linkers, rheology modifiers, surfactants, UV-absorbers, biocides, lubricants, dyes, dye-fixing agents or mordants, optical brighteners etc.
The ink jet coating may be applied to one or both substrate surfaces through conventional pre-metered or post-metered coating methods such as blade, air knife, rod, roll coating, etc. The choice of coating process would be determined from the economics of the operation and in turn, would determine the formulation specifications such as coating solids, coating viscosity, and coating speed.
The image-receiving layer thickness may range from about 1 to about 60 xcexcm, preferably from about 5 to about 40 xcexcm.
After coating, the ink jet recording element may be subject to calendering or supercalendering to enhance surface smoothness. In a preferred embodiment of the invention, the ink jet recording element is subject to hot, soft-nip calendering at a temperature of about 65xc2x0 C. and a pressure of 14000 kg/m at a speed of from about 0.15 m/s to about 0.3 m/s.
Ink jet inks used to image the recording elements employed in the process of the present invention are well-known in the art. The ink compositions used in ink jet printing typically are liquid compositions comprising a solvent or carrier liquid, dyes or pigments, humectants, organic solvents, detergents, thickeners, preservatives, and the like. The solvent or carrier liquid can be solely water or can be water mixed with other water-miscible solvents such as polyhydric alcohols. Inks in which organic materials such as polyhydric alcohols are the predominant carrier or solvent liquid may also be used. Particularly useful are mixed solvents of water and polyhydric alcohols. The dyes used in such compositions are typically water-soluble direct or acid type dyes. Such liquid compositions have been described extensively in the prior art including, for example, U.S. Pat. Nos. 4,381,946; 4,239,543 and 4,781,758, the disclosures of which are hereby incorporated by reference.